Internationally, there are increasing problems with both plastics disposal and the disposal of waste products of plastic and rubber (such as tires). At the same time, the steel industry worldwide is facing pressure to minimise its impact on the environment, for example, by reducing fuel (typically coke) consumption.
U.S. Pat. No. 5,554,207 and JP2004-052002 each disclose a process in which electric arc furnace (EAF) waste dust is combined with waste plastic to form a solid, which is then added to the EAF. On the other hand, WO2006/024069 (to the present applicant) teaches the addition of an un-agglomerated carbon-containing polymer to an EAF.
In blast furnaces, plastic charging has been proposed as a substitute fuel and to reduce CO2 emissions. Further, U.S. Pat. No. 4,175,949 discloses cutting up and charging worn pneumatic tyres into a blast furnace to replace some of the coke.
U.S. Pat. No. 5,322,544 discloses a method for melting steel using scrap metal and scrap automotive tires. In the method the scrap metal and whole scrap rubber tires are deposited in an electric arc furnace, and the whole scrap rubber tires are combusted with air or oxygen to provide an auxiliary source of heat to melt the scrap metal. This document teaches that whole scrap rubber tires are preferred so as to control combustion (ie. if shredded scrap rubber tires were used, the combustion would occur too rapidly and generate an undesirable amount of heat, and also fumes could escape from the EAF before the roof could be replaced). U.S. Pat. No. 4,175,949, on the other hand, teaches disintegrating the tires prior to charging, because excessive combustion and high heat can be accommodated (and are likely to be desirable) in a blast furnace.
US2003/0066387 discloses a process for melting steel using scrap metal and scrap rubber in an electric arc furnace. In this process, the scrap metal and scrap rubber (which can be whole, shredded or chopped) are combined and deposited into an electric arc furnace, and the rubber is combusted using oxygen or natural gas. This document teaches that the steel belts from rubber tires can be included in the scrap rubber, with the steel belts becoming part of the molten steel in the electric arc furnace. This document also teaches that whole scrap rubber tires are preferred so as to control the combustion rate.
In short, the prior art teaches that, when scrap rubber tires are introduced into a furnace, the steel present therein is also so introduced, whereby the addition of the steel is beneficial, in that it supplies additional steel to the furnace, and is not seen as detrimental.